Ubuntu announced its 9.04 release almost 18 months ago, on April 23,
2009. As with the earlier releases, Ubuntu committed to ongoing
security and critical fixes for a period of 18 months. The support
period is now nearing its end and Ubuntu 9.04 will reach end of life
on Friday, October 23, 2010. At that time, Ubuntu Security Notices
will no longer include information or updated packages for Ubuntu
9.04.

The supported upgrade path from Ubuntu 9.04 is via Ubuntu 9.10.
Instructions and caveats for the upgrade may be found at
https://help.ubuntu.com/community/KarmicUpgrades. Note that upgrades
to version 10.04 LTS and beyond are only supported in multiple steps,
via an upgrade first to 9.10, then to 10.04 LTS. Both Ubuntu 9.10 and
Ubuntu 10.04 LTS continue to be actively supported with security
updates and select high-impact bug fixes. All announcements of
official security updates for Ubuntu releases are sent to the
ubuntu-security-announce mailing list, information about which may be
found at https://lists.ubuntu.com/mailman/listinfo/ubuntu-security-announce.

Since its launch in October 2004 Ubuntu has become one of the most
highly regarded Linux distributions with millions of users in homes,
schools, businesses and governments around the world. Ubuntu is Open
Source software, costs nothing to download, and users are free to
customise or alter their software in order to meet their needs.

http://fridge.ubuntu.com/node/2132